<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div onclick="alert('hello')">
        这是一个段落
    </div>
    <script>
        
        let add=function(){
            let y=19;
            let i=1;
            let o=y+i;
            console.log(o);
        }
        u=add();
        /*let student={
            name:'syt' ,
            age:29,
            height:180,
        };
        console.log(student.name);*/
        let student=new Object();
        student.name='ystd';
        
    </script>
    <div class="box">
        abc
    </div>
    <script>
        let elem1=document.querySelector('.box');
        console.dir(elem1);
    </script>
</body>
</html>